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cute is not always enough
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Discussion Starter · #1 ·
I purchased two crank charged (wind up) lights at the dollar store. When I got home I realised that one had been opened and tampered with. Considering what I paid for it I decided it would be more fun to take it apart and see what is in it than try to return it. I found what I thought would be in there but there was more than I expected. Here is what I found.


Fig 1. Outside of the unit.​

Figure 1 shows the unit. The advertisement on the package claim the unit has two brightness settings, ability to charge other devices, a siren, and a compass. It came with some adapters for common mobile phones. It is four and one half inches long. I was attracted to the compact size but this turned out to be a drawback. I have medium sized hands and it is hard to hold the unit and crank it because it is too small. You do need to put some effort into cranking and my fingers keep slipping into the path of the crank. This prevents further cranking and, more importantly, pinches my fingers.

There are five white LEDs on the front of the unit. Brightness is achieved by lighting either just three of them or all five of them. The lamps cast a descent pool of light and are reasonably bright out to about fifteen feet. The siren is just a nuisance. Even on a good charge the noise is anemic. Part of the reason I wanted to take this thing apart was to see if I could disable it. I would not want to accidently turn it on and attract unwanted attention. The ‘compass’ is garbage. It does not reliably point in any particular direction. ‘nuf said.

I got out my tools and started to take the thing apart. It was a lot harder than I thought it would be.


Fig 2. Parts after disassembly.​

Figure 2 shows most of the bits I ended up with. On the left is the bottom part of the case with the crank attached. Next to it, mounted on a metal plate, is the 'drive train' and a generator. Next are the electronic components. Finally is the top art of the case. I just threw out some of the cosmetic silver parts and the side grip panels. The big round hole shows where the piezoelectric buzzer for the siren used to be. The unit was held together by four small screws and a large amount of glue. I am quite sure the first person to try and get into this thing did not get very far. It is very robust with all the parts firmly glued together. I had to destroy it to disassemble it. You can see some of the raged holes where I had to tear it apart.

I am sorry I was not able to get better pictures of the worky bits. My camera is old and I do not have a tripod.


Fig 3. Bottom side of internal parts​

Figure 3 shows the bottom of the internal parts. The first important thing to look at is the 'drive train'. The point of a wind up gizmo is to convert mechanical energy into electrical energy. The crank handle is mounted in the bottom half of the case. I was disappointed that there was no lubricant at all in there to grease it or prevent grit from getting in. The crank mates with the gears and they significantly increase the speed of rotation through mechanical advantage. It meshes with the large gear shown at the top of the picture and provides a gear ration is about 30:1. The generator really needs to spin fast to provide enough power. The gears and the plate they are connected to are well built. I think they are Teflon and the whole unit is very sturdy. I doubt you could easily strip the equipment with the stock crank.

The small metal gear at the bottom drives the generator on the other side of the plate.


Fig 4. Top side of internal parts​

Figure 4 shows the top side of the internal parts. The metal can shown at the bottom of the assembly on the right is the generator. It is not, technically, a dynamo. I could not get a good picture of the small visible parts inside the generator. The can is the rotor and has some kind of permanently magnetic stuff around the inside. It looks like the same kind of stuff on the back of promotional business cards they give you to stick on your refrigerator. Tucked inside the can is the stator which consists of 12 small copper coils. Barring complete destruction, I have no way of figuring out how these are connected. The output of the generator is connected to the electronics through three thin wires.

The electronics that convert the generated power into usable power and control the unit's functions are built on two circuit boards. The bottom one has two external connectors for charging other devices, the switch for selecting external or internal charging, and some discrete components. The top circuit board has more discrete components, the switch for selecting light or siren, the LEDs, and a very small integrated circuit (IC). You can also see the green battery pack that powers the lights and the siren when you are not cranking the unit.

It looks like the AC current from the generator is rectified by a bank of diodes. You can see them just to the right of the large switch on the top circuit board in figure 4. After that I am not really sure what happens. For whatever reason, the components are spread over the two boards and I cannot figure it out. Also, the components are obfuscated. The small IC on the daughter board just to the left of the switch on the top circuit board has no marking at all and the transistors markings are covered in epoxy. Someone wanted to protect their investment.

I do not know enough about electronics to be sure I have figured the circuit out but my guess is the IC and transistors are just to make the siren warble. If the selector is set to external charge the DC current from the regulator bank is fed to the external connectors. If the selector is set to internal charge the power current is fed to the battery pack and the LEDs.

I am reasonably sure the green cans in the middle are a battery bank; again, there are no markings on them. The only other option I know of would be some capacitors. I shorted the connectors with a piece of wire for a couple seconds and they maintained a charge. Capacitors would have discharged over a short.

Why is this important to survival? In the grand scheme of things maybe not so much but here are my comments.

I dislike the marketing that says these crank or shake gizmos "need no batteries" and are "good for a lifetime". Sure, you do not (can not) put batteries in them but there are only so many ways you can store electrical energy; batteries and capacitors dominate that area. These units have very small and who knows what quality batteries in them. Even the best batteries will only take a thousand charges if they are properly cared for. This system has no regulation and will probably not be used regularly so it will probably not last very long.

The case and the 'drive train' are sturdy but the electronics are shabby. The solder joints look like they were done by slave laybour. After a little handling the 'drive train' wires broke off from the circuit board. I realise taking it apart is not normal use but I would doubt these connections would survive the vibrations of a couple years in a glove compartment. I want to rebuild the important parts in a generic project box that will give me getter grip and, maybe, give me something I can rely on.

I tried charging a small iPod and it did work. However, I have no idea what damage it did in the process. There are no power regulators in the circuit. Unfortunately, I do not have an O-scope so I cannot test the output voltage or condition when using this as a crank charger. Based on my limited electronics understanding I believe the output would have significant ripple. There is no telling what this could do to sensitive electronics. In a desperate emergency situation I would use it (of course) but I would not use one on a regular basis to top up any expensive electronic gizmos.

Thank you for your time.

 

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Thanks for your time in making this post. May I ask what this unit retails for? Love the quality compass in the crank!!!!
 

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I bought a pack of 3 Husky crank lights from Home Depot for only $10.00. One of them didnt work for long (what do you expect for 10 bucks) So I broke it open and it looks exactly like what you show in your pictures. I wanted to see if there was any way to make something that would maybe charge my cellphone in a pinch. Ill let you know if I come up with anything.
 

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Thanks for tearing things apart. It is always fun.

Here is what I can tell you from what you have said and what I know of electronics. (This and 75 cents will get you a cup of coffee.)

There are 3 batteries in the pack. At 1.5 volts each, you are talking about 4.5 volts of charge.

The second board is going to be for converting the voltage from the crank to probably 6 volts for charging other electronic devices. (fairly standard output). For $15 bucks for one of them, I would like to think that this has a circuit that minimizes the warble from varied crank speeds.

I wouldn't use it for regular charging of electronic devices but it was built to be used in a pinch in the first place not in lieu of an outlet. :)

Some one with electronics skills could feasibly modify this set up to charge other batteries. Should only require some re-wiring. (I would attempt if in a real pinch but would prefer someone else that knwe more about it.)

Someone could, if they got really out there, hook this gizmo up to the back wheel of a bicycle to charge stuff up with it. (I don't see why, but iot could be done.)
 

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cute is not always enough
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Discussion Starter · #7 ·
I am pretty sure there is no regulation. Aside from the IC and the black can visible on the left in Figure 4 all the parts look like very basic bitz. There is definitely no regulator and I doubt any of the diodes are Zeners. The batteries in this thing will die relatively quickly. They are being abused during charging and will certainly not be stored in an optimal state. I would like to see about replacing them with capacitors which would have an almost indefinite life span.

The 'drive train' is well built but I doubt you could hook it up to the kind of speed and/or torque you would get off a bicycle wheel. It could be done but it would need some safeguards to prevent it from being ripped to shreds. I could also imagine the guts being rigged to 'free' power like wind or water.
 
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